Adaptation Features of Diapause Duration of the Gypsy Moth Lymantria dispar (L.) from Populations of Different Latitudinal Origination

An analysis of the influence of the sum of effective temperatures (SET) that embryos of gypsy moth (Lymantria dispar (L.)) from populations of different latitude origins receive in the midsummer—autumn period until overwintering on the diapause duration and the SET of eclosion, as well as an assessment of the effect of short-term temperature rise during the dormancy period on the eclosion duration and diapause strength, were performed. The effect of the midsummer—autumn SET on the diapause duration and on the SET of spring eclosion subject to conditions of diapause and subsequent quiescence is found. We show that a short-term rise in temperature over the embryo development threshold leads to a proportional decrease in the eclosion duration when the SET of eclosion was lower than 200 degree days. If the SET of eclosion is higher than 200 degree days, the effect of this exposure either has no effect on the eclosion duration or led to stronger dormancy. A short-term temperature rise leads to an increased mortality of embryos that receive a low midsummer—autumn SET (approximately 400–450 degree days with a threshold of approximately 7°C). Embryos that receive a high midsummer—autumn SET (approximately 1300–1500 degree days with a threshold of approximately 7°C) show no increased mortality. On the basis of these results, we assume that the populations of southern origination have a stronger diapause due to the adaptation to the short-term casual temperature rise above the embryo development threshold in the winter—spring period, which may lead to the premature eclosion of gypsy moth larvae.